The use of microwave ovens for quickly and conveniently heating and cooking foods has become commonplace and continues to grow. The increased use of frozen microwaveable food propels that growth even further because of the lack of desire or time to spend in cooking food. The speed in the preparation and serving of complex frozen dishes; the ability to microwave ready-to-eat food; and the steady improvement in the quality and diversity of fast food, not only in the home, but also within the great fast food outlets, has led to considerable effort being expended to upgrade food compositions and products to make them more suitable for shipping, handling, packaging and cooking.
However, microwave cooking is known to be unsatisfactory for a variety of foods, especially those that require browning or crispening by surface heating. A number of methods and containers have been used; however, a variety of problems have not been adequately addressed such as the food adhering to the film or container, the need to flavor or add fragrance to the food, or the need to easily form a cooking package with food wrap.
There have been considerable improvements in microwave cooking and packaging technology in the past two decades. Microwave cooking is fast, efficient and economical in contrast to infra-red cooking; however, microwave cooking has several disadvantages. Primarily, it cannot crisp, brown and optionally add flavors or fragrances to food such as chicken, doughy products, frankfurters, hamburgers, steaks, pizza, etc. It is known that the fundamental reason for this is that microwaves cook food from the inside out whereas infra-red cooks from the outside in.
Various attempts have been made to correct for the inherent lack of browning and crispening such as physical modifications to the microwave oven, the addition of edible coatings to the food, and the use of a variety of preformed cooking packages, dishes and the like.
It is known that a thin metal film, such as, but not limited to, aluminum, can absorb substantial amounts of microwave energy and convert this energy into thermal energy for heating a variety of food products. These thin metal films, commonly called susceptors, are associated with conductive and infra-red heat transfer to the food product. The food still tends to stick to these containers.
Some of the prior art patents pertaining to microwave cooking include the following patents:
U.S. Pat. No. 5,231,268 discloses a four layered paperboard, semirigid packing material for use in manufacturing containers. In this instance, a paperboard substrate was coated with a thermal insulator, e.g., sodium silicate, followed by a printable, aqueous susceptor-ink layer (graphite in a sodium silicate vehicle), and a thermal barrier layer to facilitate release of water vapor from the layers. Neither the use of a non-stick coating, nor flavoring and/or fragrance nor an aluminum coating were utilized. The package was also preformed.
U.S. Pat. No. 4,267,420 pertains to a four layered, preformed structure comprising a polymer film with vacuum deposited aluminum susceptor, an adhesive layer and a second polymer layer preferably polyethylene. There was no non-stick layer and two polymeric film layers are used.
In the present invention one polyester film layer and one susceptor layer on paper film in addition to an adhesive layer (preferably FDA approved) and a non-stick layer (preferably FDA (approved) that can be optionally modified to add flavor and fragrance are used because this combination imparts the desired dimensional stability, the non-stick properties, the browning and crispening. Moreover, the present invention allows the package to be easily custom formed by the user. Prior art U.S. Pat. No. 5,231,268 utilizes various layers to release water vapor produced during the cooking. This does not prevent food from sticking to the container, but does include a susceptor layer and thermal insulators such as sodium silicate.
Prior art U.S. patents in the general area of which we are aware include: U.S. Pat. Nos. 4,641,005 and 4,825,025.
Accordingly, it may be appreciated that the prior art relates to preformed, rigid paperboard containers, manufactured at a factory, filled with food at another factory, transported to a retailer, stored in the package and finally purchased as a package ready for use in a microwave oven for cooking.